Exporting and DPI, does it matter?

I'm SO sorry if this has been posted, but I've been trying to read up on this for the past 4 hours with a crying teething baby so I'm resorting to asking on my own specific thread. Thank you to anyone willing to help me out!!!

My cousin wants to print a 24" x 36" canvas. My pixels for the image are 2484 x 2321. If my understanding is correct, i could not print this at 300 dpi, it would have to be closer to 100 dpi, right? But if I export all my photos for my cousin at 300 dpi, will the printer be able to still print it, or do I have to, for bigger prints, select a smaller dpi for export.

Also, why doesn't the file size change at all when I select different DPI?

One last little question too, when selecting image quality I have read that above 10 is not perceivable. REally? Even in a big canvas? It makes the files enormous, but if I selected 12 there would be no visible difference even at that large?

(btw, processing with aperture 3)

DPI is just a number inside a file, it's irrelevant in most cases. What's important is the number of pixels.

Go ahead and print the canvas with the file you have, it should look fine. Though 2484 x 2321 pixels is almost square, and it won't fit a 24x36" canvas.

Oh dear. I meant it is: 3484 x 2321. This is what the guy at mix said:

The dpi must be set to a minimum of 250. *In order for the item to be printed as a 24x36, it must be sized at at least 2400x3600. *With this file, you would not be able to print a size this large.

Why would the dpi matter? Don't they set the dpi? And if so wouldn't a 2400 x 3600 local be printed at 100 dpi to make it 24 x 36 inches?

Most print guys don't have a clue. It's easier to meet their senseless requirements than it is to eduate them.

In Photoshop use image -> resize, enter 300 in the ppi field, make sure the resample checkbox is checked.

MelissaHaws wrote in post #15110332
wouldn't a 2400 x 3600 local be printed at 100 dpi to make it 24 x 36 inches?

See, you already know more about dpi and printing than the moron at the print shop! Yes, you are totally correct.

I'm afraid I've never used Aperture, so I don't know the export options. However, this is what you need to do to satisfy the pointless demands of the print-shop moron.

Resize your image to 9000 x 6000 pixels, 36x24 inches and 250 dpi. I suspect you'll only need to change two of those, because the third is dependant on the other two. Then export it as a jpeg. You won't need top-quality, especially for a canvas print.

Personally I'd email the print-moron and explain why I was using a different printer.